Method of identification of an element in two or more images

ABSTRACT

The present invention relates to a method and an apparatus for identification of an element in two or more images. The method comprises the steps of, identifying, in an image an integral three-dimensional element visible in the image, and identifying in a first image the three-dimensional element, identifying in a second image the three-dimensional element. Subsequently, collating is performed based on the first image and the second image and based on a determination of the position of the three-dimensional element in the first image and the position of the three-dimensional element in the second image. Thereby, a position and/or an extension in three dimensions of a bodily matter of interest within the human body or the animal body may be established.

FIELD OF INVENTION

The present invention generally relates to a method for identifying anelement common in two or more images and subsequently collating the twoor more images based on the common element. The present inventionspecifically relates to a method for identifying an element beingpositioned in a human body or an animal body in relation to bodilymatter such as a tissue or an organ or other bodily matter.

The invention may also relate to establishing a bodily parameter such astemperature, blood flow, nerve impulses or other bodily parameters ofinterest within the human body or the animal body. The bodily parameteris established based on identifying the element in relation to thebodily matter of interest.

BACKGROUND

A problem associated with the prior art medical imaging techniquesconcerns the accurate selection and comparison of views of identicalareas in images that have been obtained by imaging equipment atdifferent times or by images obtained essentially at the same time usingdifferent image modalities, e.g., CT, MRI, SPECT, and PET, or by imagesobtained essentially at the same time using different set-up conditions.This problem has two aspects.

First, in order to relate the information in an image of the anatomy tothe anatomy itself, it is necessary to establish a one-to-one mappingbetween points in the image and points on the anatomy. This is referredto as registering image space to physical space.

The second aspect concerns the registration of one image space toanother image space. The goal of registering two arbitrarily orientedimages is to align the coordinate systems of the two images such thatany given point in the scanned anatomy is assigned identical addressesin both images. The calculation of the rigid body transformationnecessary to align images requires knowledge of the movement androtation of the anatomy in the images.

Calculation of the rigid body transformation of the anatomy for planaralignment of the coordinate systems of two-dimensional images requiresknowledge of the coordinates of either at least two single points or aline in the images. Calculation of the rigid body transformation of theanatomy for three-dimensional alignment of the coordinate systems ofthree-dimensional images or multi angle two-dimensional images requiresknowledge of the coordinates of either at least three single points, twolines in the images or a three-dimensional object in the images.

Single identifiable points marking identical locations in the images arecalled “fiducial points” or “fiducials,” and the fiducials used are thegeometric centres of markers, which are called “fiducial markers”. Thesefiducials are used to correlate image space to physical space and tocorrelate one image space to another image space. The fiducial markersprovide a constant frame of reference visible in a given imaging mode tomake registration possible.

One problem extant in the field lies in the provision of fiducialscapable of use with several imaging modalities. MRI and X-ray CT imagesare digital images, in which the images are formed point by point. Thesepoints are called picture elements, or pixels, and are associated withan intensity of light emitted from a cathode ray tube, or are used toform an image on film. The array of lighted pixels enables the observerto view an image.

The manner in which the intensity of any given pixel is altered ormodulated varies with the imaging modality employed. In X-ray CT, suchmodulation is a function primarily of the number of electrons per unitvolume being scanned. In MR imaging, the parameters primarilyinfluencing this modulation are the proton spin density and longitudinaland transverse relaxation times T1 and T2, which are also known as thespin-lattice and spin-spin relaxation times, respectively.

By using and combining different imaging modalities, one can benefitfrom the characteristics of the different modalities, facilitating somein-body objects being clearer and easier to identify in one imagemodality than in another and vice versa. Hereby improved identificationof in-body objects and improved diagnosis is facilitated.

In constructing a fiducial marker, one must be aware that an agent thatcan be imaged under one imaging modality will not necessarily beimageable under another modality. And yet, the ability to image underboth CT and MRI with a given marker would be especially useful, in thatone would then be able to register images derived from different imagingmodalities. For example, the capability to register CT and MR imageswould allow the integration of information concerning bony structureprovided by a CT scan with the soft tissue anatomical informationprovided by an MRI scan. There remains a need for a fiducial marker thatcan be used to establish a known coordinate system under several imagingmodalities, and which facilitates anatomical alignment of the differentimages.

A further problem in the field arises from the competing needs ofaccommodating patient comfort, which would tend to lead clinicianstoward the minimization of marker size, for a less traumaticimplantation process, with the desire of clinicians to use markers thatare as bright and thus as large in the images as possible. Suchbrightness is desirable because it provides a strong signal that can bedistinguished from noise inherent in the imaging process. The use oflarge-sized markers is also desirable so that the image of the markeroccupies as many full pixels as possible. Increasing the number of fullpixels occupied by the marker increases the accuracy with which theposition of the marker can be determined, and the safety that thefiducial point can be clearly identified and is not mixed up with otherpoints in the images.

Furthermore, the general technique of using fiducial markers requiresthe determination of the centroid of the marker; it is easier to computethe centroid for a large, bright marker than for a smaller, dimmermarker. On the other hand, the larger the marker of the prior art is,the more difficult it is for the patient to tolerate its presence forextended periods of time when the marker is buried in the tissue. Thereremains a need for a marker which can exploit the advantages presentedby increased size that would also be tolerated by the patient during theperiod of its use. There is also a need for a small multi-modalitymarker that can be implanted into a patient and remain there for moreextended periods of time, without harming the patient.

Furthermore there is a need for a single marker that can provideinformation on the coordinates of at least three points within thedifferent images.

Such a more permanent fiducial marker would preferably be detectable bya non-invasive technique so that its position in physical space could bedetermined and its centroid computed even as it remains hidden fromvisual inspection beneath the patient's skin.

U.S. Pat. No. 6,333,971 describes an implantable fiducial marker havinga sealed cavity for the introduction of an imaging agent that providesimaging capability in several modes, including Computed Tomographicimaging (CT) and Magnetic Resonance Imaging (MRI). The marker may bepermanent, or it may be temporary and readily detachable from its anchorsite. Combinations or agents imageable under CT scanning are combinedwith agents imageable under MRI scanning. The choice of imaging agentsallows for the construction of a marker that is visible under both CTand MRI imaging modalities. Furthermore, by using a marker thatcomprises a solid outer portion and an aqueous inner portion, the markercan be located through the use of a non-invasive transcutaneousdetection system, such as one employing ultrasound to detect thepresence of the solid-liquid interface between the aqueous core and thesolid outer portion. The use of solid metal is eschewed throughout. Thepresence of metal may cause unwanted artefacts and image distortion inthe image, and may impede efforts to localize the marker.

Visicoil™, a product from Radiomed Corporation in the USA, consists inlinear fiducial markers that are naturally visible by ultrasound, X-Ray,CT, MRI, and high-energy photons (portal images), allowing thephysicians to implant the markers under one mode and later visualizethem by another technique for treatment planning. Visicoil™ markers canbe more easily recognized than the much larger point markers and withless confusion. Two or more Visicoil™ markers is needed for providingthree-dimensional volume information. The Visicoil™ markers have to beimplanted into the tissue of interest by invasive surgery and theVisicoil™ technique needs at least two markers for establishing an exactdetermination of a location of the tissue of interest. Thus, both theinvasive surgery and the implantation of two or even more markersincrease the risk of trauma to the patient.

One example of applications benefiting from alignment of differentimages is in relation to treatment of cancerous lesions in the humanbody irradiation of the disordered tissue, such as a tumor, is used inorder to destroy the disordered tissue. The disordered tissue may beplaced in all parts of the body. When the disordered tissue ispositioned in some parts it may be difficult to irradiate withoutcrucially damaging other essential parts of the body and in some casesthe irradiation can cause irreversible damage.

Thus, the irradiation of the disordered tissue is restricted by theamount of irradiation, which healthy tissue may tolerate without beingcrucially or irreversible damaged. This limitation of the irradiation isfurther increased by the fact that it may be difficult to preciselylocate the disordered tissue and to determinate the extension of thedisordered tissue inside the body.

Due to the fact that different diagnostic imaging technologies result indifferent parts and organs of the patient's body to be clearlyidentified, a combination of different imaging technologies such as CT,MR, PET, SPECT, X-ray, High-voltage X-ray is often used for localisationof the bodily matter of interest (e.g. a cancerous tumor being thetarget for irradiation. The different images might be merged in a fusionof two or more images using data processing equipment. By combining thedifferent imaging technologies a more accurate identification andlocalisation of a bodily matter of interest is possible, e.g. acancerous tumour. In order to make the identification and localisationof the bodily matter of interest accurate, the images need to be alignedaccurately near the bodily matter of interest.

A combination of different images, generated by different imagingtechnologies is for example used during the planning of radiationtherapy. During the planning of radio therapy, the cancerous tumour isidentified in diagnostic images, e.g. CT, MR, PET, SPECT, X-ray.Hereafter position and form of the tumour is localised and a profile ofthe irradiation to be given to the patient is generated, based on theform and position of the tumour.

Diagnostic images made with different imaging technologies and differentapparatuses are often obtained with a time interval between the images,and with the patient repositioned on a different couch for each image.This results in different set-up conditions for each image. Thedifferent set-up conditions result in a difference between the actualpositions of the bodily matter of interest inside the body of thepatient in the different images, compared to visual objects in theimages (bone structures, outer surface of the patient's body etc.),placed a distance from the bodily matter of interest. The differencebetween the positions of the bodily matter of interest in the differentimages can occur either by internal organ motion inside the patient'sbody and/or by inaccurate positioning of the patient under the imagegenerating equipment.

Today, fusion between different diagnostic images is often aligned byusing anatomic markers, which are visual in the different diagnosticimages (bone structure, outer surface of the patient's body etc.). Thoseanatomic markers are often positioned a distance from the bodily matterof interest. Due to the fact that the bodily matter of interest willoften have made a relative motion, compared to the anatomic markerspositioned a distance away from the bodily matter of interest, analignment of the different images based on the anatomical markers willresult in inaccurate alignment of the images near the bodily matter ofinterest.

Alternatively fusion between the different diagnostic images can bealigned according to implanted fiducial markers or implanted linemarkers. Other factors which can lead to inaccurate alignment of theimages are differences in the set-up conditions for the imagingequipment or the patient (e.g. the images are not obtained in exactlythe same angle, and/or the image quality is not identical in theindividual images (the image quality does often depend on the focalpoint).

A combination of different images can also be used for setting uptreatment apparatuses, for example an irradiation equipment for externalbeam radio therapy of a cancerous tumor. The irradiation target islocalised in at least one reference image during a planning session,prior to the treatment session. When starting a treatment session thetreatment apparatus can be set up based on fusion between the referenceimage and an image obtained just before treatment or during treatment.

U.S. Pat. No. 5,853,366 describes a system to be used for radio therapyof a tumor. The location of the tumor is performed by inserting at leastthree markers in relevant positions around the periphery of the tumor.These markers are made from stainless steel capable of being detected ina conventional X-ray image of the body in order to position theirradiation source in relation to the tumor before irradiation of thetumor. Each marker is depicted as one point in an X-ray image. Thesemarkers are inserted directly into the tissue surrounding the tumor andthe markers are barbed or V-shaped in order to securely fasten themarkers into the tissue thereby inhibit movement of the markers.Subsequently to positioning of the markers and irradiation of the tumor,the barbed markers have to be removed by invasive surgery.

WO 99/27839 discloses a system for positioning and repositioning of aportion of a patient's body with respect to a treatment or imagingmachine including multiple cameras to view the body and the machine.Index markers placed externally on the patient's body, eitherlight-emitting, passive, geometric shapes, or natural landmarks, areidentified and located by the cameras in 3D space. Anatomical targetsdetermined from image scanning can be located relative to referencepositions associated with the treatment or diagnostic machine. Severalforms of camera, index markers, methods and systems accommodatedifferent clinical uses. X-ray imaging of the patient further refinesanatomical target positioning relative to the treatment or diagnosticimaging reference point. Movements of the patient based on comparativeanalysis of imaging determined anatomical targets relative to referencepoints on treatment or diagnostic apparatus are controlled by the systemand process.

WO 02/19908 discloses a method and an apparatus for compensating forbreathing and other motions of the patient during treatment, the methodcomprising: generating images of the target region prior to thetreatment; periodically generating positional data about the internaltarget region based on markers implanted in the patient's body;continuously generating positional data about external motion of thepatient's body using one or more external sensors; and generating acorrespondence between the position of the internal target region andthe external sensors so that the treatment is directed towards theposition of the target region of the patient based on the positionaldata of the external sensors. The target region's position issubsequently matched to the position of the target region in thepreoperative images.

WO 02/100485 discloses a system and method for accurately locating andtracking the position of a target, such as a tumor or the like, within abody. In one embodiment, the system includes one or more excitablebeacons positioned in or near the target, an external excitation sourcethat remotely excites the beacons to produce an identifiable signal, anda plurality of sensors spaced apart in a known geometry relative to eachother. A computer is coupled to the sensors and configured to use thebeacon signals to identify a target isocenter within the target. Thecomputer compares the position of the target isocenter with the locationof the treatment isocenter. The computer also controls movement of thepatient and a patient support device so the target isocenter iscoincident with the treatment isocenter before and during radiationtherapy.

Markers as described above are used to define the extent of a disorderedtissue area, and/or to guide the treatment equipment, but still thewhole area may be difficult to view in the image. For this reason andother reasons when planning irradiation of disordered tissue, themedical practitioner or the attending physician plans the irradiation byapplying an irradiation margin in order to be sure that all of thedisordered tissue area is irradiated. This margin results in some of thehealthy tissue being deliberately irradiated and therefore theaforementioned crucial damages may occur. Also, only fiducial markersare disclosed. A fiducial marker itself provides no possibility ofidentifying any rotation of the marker. Fiducial markers provide nopossibility of localizing the disordered tissue without having at leasttwo, and as disclosed, preferably three fiducial markers employed.

Further reasons for applying the irradiation margin is the inaccuracy inpositioning the patient below the irradiation equipment, the inaccuracyof the resolution of the derived image of the disordered tissue and thefact that the internal organs may move over time. Such movement of theinternal organs may be caused by respiration and/or by day-to-daymovements. The use of implanted markers for guiding the treatment asdescribed above can, to some extend, improve the accuracy of thepositioning of the patient.

U.S. Pat. No. 6,307,914 discloses a moving body pursuit irradiatingdevice comprising a linac for controlling the irradiation of a medicaltreatment beam to a tumor, and a tumor marker buried in the vicinity ofthe tumor, a first X-ray fluoroscope for picking up an image of saidtumor marker from a first direction, and a second X-ray fluoroscope forpicking up the image of said tumor marker from a second direction at thesame time as said first X-ray fluoroscope, first and second recognitionprocessing sections which execute template matching at a real time levelat a predetermined frame rate by a shading normalization mutualcorrelation method for applying a template image of the tumor markerregistered in advance to image information digitized by said first andsecond image input sections, and calculate first and secondtwo-dimensional coordinates of said tumor marker, a central arithmeticprocessing section for calculating three-dimensional coordinates of saidtumor marker from the first and second two-dimensional coordinatescalculated by said first and second recognition processing sections; andan irradiating control section for controlling the irradiation of themedical treatment beam of said linac by said calculatedthree-dimensional coordinates of the tumor marker.

Implanted markers of prior art that is positioned in the body of thepatient are buried in tissue and therefore require invasive surgery tobe inserted in the body as well as further subsequent invasive surgeryto be retracted from the body.

Diagnostic images made with different imaging technologies and withdifferent medical imaging equipment can be derived with a time intervalbetween the images, and with the patient repositioned on a differentcouch for each image. This results in different set-up conditions foreach image. The different set-up conditions result in a differencebetween the actual position of the tissue of interest inside the body ofthe patient in the different images, compared to visually clear objectsin the images, placed a distance from the tissue of interest, such asbone structures, outer surface of the patient's body etc. The differencebetween the positions of the tissue of interest in the different imagescan occur either by internal organ motion inside the patient's bodyand/or by inaccurate positioning of the patient below the medicalimaging equipment.

A need exists however of an improved marker and a method for collatingdifferent images obtained by different imaging equipment, and/orobtained with a time interval between the images, and/or obtained withdifferent set-up conditions for the images, in order to at least partlyovercome the aforementioned disadvantages of the prior art relating tolocalizing the tissue of interest. An improved marker is a marker easyto detect and sufficiently precise to detect in different imagingequipment. An improved marker may alternatively or additionally be amarker easy to implement into and/or easy to retract from the human oranimal body.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a method forovercoming the disadvantages and drawbacks of the known methods andsystems presented above.

These objectives and the advantages that will become evident from thefollowing description of the invention are obtained by the followingembodiments and aspects of the method according to the present inventionby providing a method for identification of an element in two or moreimages, the method comprising the steps of,

-   -   identifying, in an image, at least one integral        three-dimensional element visible in the image, said at least        one integral three-dimensional element being in position in        relation to a bodily matter of interest within a human body or        an animal body, the method comprising the steps of:    -   identifying in a first image the three-dimensional element,        visible in the first image,    -   identifying in a second image the three-dimensional element,        visible in the second image,    -   collating the first image and the second image based on a        determination of the position of the three-dimensional element        in the first image and the position of the three-dimensional        element in the second image, and

A method according to the invention, employing an improved marker, saidmarker possible being a single marker with at least three identifiablepoints, results in knowledge not hitherto obtainable about movementand/or rotation and/or change of shape and/or change of extension of thetissue or the organ of interest, preferably in three dimensions.

With the three-dimensional element being positioned and fixed inrelation to a bodily matter of interest a mutual positional relationshipbetween the three-dimensional element and the bodily matter of interestcan be established. The knowledge about the position of thethree-dimensional element in the image gives an exact knowledge of wherethe bodily matter of interest is positioned, because the bodily matterof interest and the three-dimensional element have been found to have asubstantially fixed relationship and any possible movement of the bodilymatter of interest results in corresponding movement of thethree-dimensional element and vice versa. Images can be alignedaccording to the three-dimensional element and hereby also bodily matterof interest will be aligned in the images.

In the context of the present invention, bodily matter is to beconstrued as any matter relating to the body, e.g. any of the differentbody organs, body tissue including abnormal body tissue such as a tumoror body substances such as ascites, bile, blood, cerebrospinal fluid,lymph or urine, etc.

In the context of the present invention, tissue is defined as cellsgrouped together in the body to form tissues, i.e. a collection ofsimilar cells that group together to perform a specialized function.Four primary tissue types are defined in the human body:

Epithelial tissue—The cells of epithelial tissue pack tightly togetherand form continuous sheets that serve as linings in different parts ofthe body. Epithelial tissue serves as membranes lining organs andhelping to keep the body's organs separate, in place and protected. Someexamples of epithelial tissue are the outer layer of the skin, theinside of the mouth and stomach, the intestines and the tissuesurrounding the body's organs, the respiratory epithelium and theendothelium of the various blood vessels.

Connective tissue—Generally speaking, connective tissue adds support andstructure to the body. Most types of connective tissue contain fibrousstrands of the protein collagen that add strength to connective tissue.Some examples of connective tissue include the inner layers of skin,tendons, ligaments, cartilage, bone and fat tissue. In addition to theseforms of connective tissue, bone is also considered a form of connectivetissue.

Muscle tissue—Muscle tissue is a specialized tissue that can contract.Muscle tissue contains the specialized proteins actin and myosin thatslide past one another and allow movement. Examples of muscle tissue arecontained in the muscles throughout the body.

Nerve tissue—Nerve tissue contains two types of cells: neurons and glialcells. Nerve tissue has the ability to generate and conduct electricalsignals in the body. These electrical messages are managed by nervetissue in the brain and transmitted down the spinal cord to the body.

In the context of the present invention, organs are defined as astructure containing at least two different types of tissue functioningtogether for a common purpose. The different body organs may be ofinterest imaging for the purpose of diagnosis and/or therapy and/orsurgery. There are ten major organ systems in the human body:

Skeletal system: The skeletal system is providing support for the body,to protect internal organs and to provide attachment sites for theorgans. Major skeletal system organs are bones including the skull,cartilage, tendons and ligaments.

Muscular system: The muscular system providing movement. Muscles work inpairs to move limbs and provide the organism with mobility. Muscles alsocontrol the movement of materials through some organs, such as thestomach and intestine, and the heart and circulatory system. Majormuscular system organs are skeletal muscles and smooth muscles.

Circulatory system: The circulatory system is transporting nutrients,gases (such as oxygen and CO₂), hormones and wastes through the body.Major circulatory system organs are the heart, blood vessels and theblood.

Nervous system: The nervous system is transmitting electrical signalsthrough the body. The nervous system directs behaviour and movement and,along with the endocrine system, controls physiological processes suchas digestion, circulation, etc. Major nervous system organs are thebrain, the spinal cord and the peripheral nerves.

Respiratory system: The respiratory system is providing gas exchangebetween the blood and the environment. Primarily, oxygen is absorbedfrom the atmosphere into the body and carbon dioxide is expelled fromthe body. Major respiratory system organs are the nose, trachea and thelungs.

Digestive system: The digestive system is breaking down and absorbingnutrients that are necessary for growth and maintenance. Major digestivesystem organs are the mouth, esophagus, the stomach, small and largeintestines.

Excretory system: The excretory system is filtering out cellular wastes,toxins and excess water or nutrients from the circulatory system. Majorexcretory system organs are the kidneys, ureters, the bladder andurethra.

Endocrine system: The endocrine system is transmitting chemical messagesthrough the body. In conjunction with the nervous system, these chemicalmessages help control physiological processes such as nutrientabsorption, growth, etc. Many glands exist in the body that secreteendocrine hormones. Among these, the major endocrine system organs arethe hypothalamus, pituitary, thyroid, pancreas and adrenal glands.

Reproductive system: The reproductive system is producing cells thatallow reproduction. In the male, sperm are created to inseminate eggcells produced in the female. Major female reproductive system organsare the ovaries, oviducts, the uterus, vagina and mammary glands. Majormale reproductive system organs are the prostate, the testes, seminalvesicles and the penis.

Immune system: The immune system is destroying and removing invadingmicrobes and viruses from the body. The lymphatic system also removesfat and excess fluids from the blood. Major immune system organs arelymph, lymph nodes and vessels, white blood cells, T- and B-cells.

According to a possible method according to the invention, the methodfurther comprises a step of

-   -   establishing a position and/or establishing an extension of a        bodily matter in the human body or the animal body, the        establishing being based on collating the first image and the        second image.

According to the present invention, each individual image may be a twodimensional projection image or a three-dimensional image, and whereinthe image is derived and processed by medical imaging equipment.

According to the invention the steps of identifying thethree-dimensional element and collating the images based on thedetermination of the position of the three-dimensional element in theimages may be performed in more than two images.

According to the invention the steps of identifying thethree-dimensional element and collating the images based on thedetermination of the position of the three-dimensional element in theimages may be performed in images obtained by different imagingmodalities.

According to the invention the steps of identifying thethree-dimensional element and collating the images based on thedetermination of the position of the three-dimensional element in theimages may be performed in images obtained with different set-upconditions (e.g. images obtained from different angles, or imagesobtained with a deliberate or an undeliberate movement of the patientand/or of the tissue of interest (and hereby a movement of thethree-dimensional element) between the images).

According to the invention the steps of identifying thethree-dimensional element and collating the images based on thedetermination of the position of the three-dimensional element in theimages may be performed in images obtained with a time interval betweenthe images being obtained, potentially resulting in different set-upconditions in the images, and/or movement of the tissue of interest (andhereby a movement of the three-dimensional element) within the humanbody or the animal body between the images.

Given a possibility to align different images more exactly than by theprior art methods, facilitates the possibility to track a developmentover time, within images obtained at different times. Tracking adevelopment over time, within images obtained at different times,facilitates tracking of movement and/or growth/shrinking of bodyelements, in general called bodily matter, for better diagnosis (e.g.tracking of the growth of a cancerous tumor or tracking of the movementof a cancerous tumor according to the patient's breathing cycle).

Examples of applications which might benefit from exact alignment ofdifferent images are:

Collating images (obtained by different imaging technologies and/orobtained in different planes/angles). Collating images (obtained bydifferent imaging technologies and/or obtained in differentplanes/angles) by the method according to the invention, andincorporating use of a three-dimensional element as a marker, results inimproved identification of bodily matter and the better identificationresults in a better diagnosis.

Possible use applications in relation to collating images by a methodaccording to the invention may be the following non-exhaustive list ofapplications:

-   -   Reduction of inaccuracies due to set-up differences between the        images    -   Identification of unwanted in-body elements (e.g. position and        size of cancer tumors, position and size of encrustations or        stone-formations, position and size of foreign bodies or one or        more fetuses)    -   Planning of treatment and/or identification of treatment target        (e.g. planning of irraditation treatment)    -   Identification and/or diagnosis of orthopaedic damages (bone        fractures, joint fractures or joint dislocations)    -   Identification of possible obstructions of bodily lumens (e.g.        urothelial obstructions due to encrustation or foreign bodies,        cardiovascular obstructions due to encrustation, etc.)

Further examples of applications which might benefit from exactalignment of different images are:

Comparing images (obtained at different times. comparing a present imagewith a reference image). Comparing images by the method according to theinvention, and incorporating use of a three-dimensional element as amarker, results in tracking of progress of movement and/orgrowth/shrinkage of a bodily matter of interest.

Possible use applications in relation to comparing images by a methodaccording to the invention may be the following non-exhaustive list ofapplications:

-   -   Tracking of growth or shrinkage of a cancerous tumor.    -   Tracking of growth or shrinkage of a cardiovascular lumen.    -   Tracking movement of a foreign body, a parasite or the like.    -   Correction of inaccuracies due to set-up differences between        obtaining the reference image and obtaining the present image.    -   Correction of inaccuracies due to internal body organ movements        between obtaining the reference image and obtaining the present        image.    -   Tracking internal body organ movements.

The correction of inaccuracies due to set-up differences and/or due tointernal body organ movements, and/or the tracking of internal bodyorgan movements may be established for different reasons, such as:

-   -   Controlling external treatment equipment according to linear        movement and rotation of the treatment target (e.g. guiding an        irradiation equipment).

According to a possible method step according to the invention,subsequent to establishing a position of a bodily matter of interestand/or establishing an extension of a bodily matter in the human body orthe animal body, a bodily parameter is derived based on establishing theposition and/or the extension of the bodily matter.

In the context of the present invention, bodily parameters are to beconstrued as any parameter related to the body, e.g. physiologicparameters such as temperature, bodily fluid parameters such as flow ofascites, bile, blood, cerebrospinal fluid, lymph or urine flow, bodilyelectrochemical parameters such as nerve impulses, etc.

Combination of different images, generated by different imagingtechnologies, and/or generated under different set-up conditions may beused during the planning of therapy or surgery. During the planning oftherapy or surgery, a bodily matter of interest, such as an organ ofinterest, e.g. the prostate, or such as a tissue of interest, e.g. acancerous tumor, or such as a substance of interest, e.g. urine, isidentified in diagnostic images. Hereafter position and shape of thebodily matter is localised and the specifications of the therapy orsurgery to be given to the patient is generated, based on the shapeand/or position and or extension of the bodily matter.

Any inaccuracy of the identification of the bodily matter during theplanning of therapy or surgery will result in inaccuracy during thetreatment or surgery, resulting in a risk that the therapy or surgerydoes not effect the intended bodily matter of interest. Possibly, it mayresult in a traumatic effect of healthy matter and/or it may result inpart of the unhealthy matter not being treated or not being properlyhandled during treatment.

By deriving at least a first image and a second image, and by collatingthe images by determining the position of the three-dimensional element,the three-dimensional element and hereby the bodily matter of interestwill be identically positioned in the images. Thereby, the possibleadvantages of the first type of medical imaging equipment and thepossible other or additional advantages of the second type of medicalimaging equipment will be obtained at the one and same time in respectof the mutual positional relationship between the three-dimensionalelement and the bodily matter of interest. Additionally or alternativelyinaccuracies in the alignment of the images resulting from differentset-up conditions, when obtaining the images, may be compensated.

By using a three-dimensional element as marker being positioned inside,or at least in close vicinity of the bodily matter of interest, theimages can be collated very accurately near the marker, and hereby nearthe bodily matter of interest. Hereby it is possible to collate theimages accurately based on the position, in the images, of thethree-dimensional element, hereby ensuring that the position and/or theshape and/or the extension of the bodily matter of interest, beingpositioned in an accurate position in relation to the three-dimensionalelement, is also determined accurately in the images.

By using a three-dimensional element as marker being positioned inside,or at least in close vicinity of the bodily matter of interest, it isfurthermore possible to compensate for different image quality in theimages. Often the image quality in one image is depending on the focalpoint of the image. By collating the images according to athree-dimensional element located inside or near the tissue of interest,improved compensation of different image quality in the images isfacilitated and/or improved compensation of different image quality indifferent parts of each individual image is facilitated.

Given the more accurate determination of the position and/or the shapeand/or the extension of the bodily matter of interest in the differentimages of the different medical imaging equipment, a physicist and/ormedical personnel will be able to identify and localise the bodilymatter of interest, such as a cancerous tumor, very accurately.

Contrary hereto, when trying to compare images that are derived bydifferent medical imaging equipment, according to prior art methods, themutual positional relationship between a marker and the bodily matter ofinterest is not possible to establish accurately due to the fact of themarker, either not being present in the human or animal body, or themarker not being positioned in a position ensuring a constant mutualrelationship between the position of the marker and the position of thebodily matter of interest.

By using a marker that is a three-dimensional element, such as atubular, endoluminal prosthesis with a well known three-dimensionalgeometry, the collation of the different images can be guided by anautomatic detection of the three-dimensional element in the differentimages, hereby making it possible to automatically guide the collationof the position, in the different images, of the three-dimensionalelement and thus of the bodily matter of interest.

If the dimensions of the three-dimensional element are known in advance,the dimensions of the three-dimensional element give an exact knowledgeof how the three-dimensional element is positioned inside the body andperhaps is being rotated inside the body. By knowing the dimensions ofthe three-dimensional element in advance and by being able to detect thedimensions in an image, the exact position of the three-dimensionalelement inside the body may be calculated automatically. The knowledgeabout the position of the three-dimensional element established in theimage gives also an exact knowledge of where the bodily matter ofinterest is positioned, because the bodily matter of interest and thethree-dimensional element have a substantially fixed relationship andany possible movement of the bodily matter of interest results incorresponding movement of the three-dimensional element and vice versa.

Hereby, alignment of the images and of the bodily matter of interestdepicted in the images may be performed accurately and automaticallybased on the position of the element even though the patient and/or theimage equipment has been moved between the image sessions or has movedjust before setting up the patient and the imaging equipment.

It is likewise possible during a treatment of the patient to adjust atreatment equipment so that the element and thereby the bodily matter ofinterest, such as a tumor, of the patient stays in focus of thetreatment equipment.

By being able to adjust the treatment equipment based on the element,the treatment may be performed more precisely and the adjustment of thetreatment equipment may be done automatically by a computer.

Additionally, the method according to the present invention may furthercomprise the steps of:

-   -   monitoring over time a possible movement of the        three-dimensional element in relation to the images,

A monitoring over time of the movement of the three-dimensional elementand hereby of the bodily matter of interest facilitates a constantalignment of images and/or a calculation of a cyclic movement of thebodily matter of interest (e.g. due to respiration) and/or a constantequalizing of a treatment apparatus, whereby an improved treatment ispossible. Such a tracking can be calculated and controlled by acomputer.

The steps of identifying, establishing, monitoring and adjusting may bedone automatically, and the monitoring step may be executed at anappropriate frequency, such as once every 3 seconds or less depending onthe equipment available.

Monitoring of the movement of the three-dimensional element mayaccording to the present invention be performed by producing up to 50images per second, at least 2-50 images per second, at least 1 image persecond, at least 12 images per minute or at least 2 images per minutedepending on the medical imaging equipment, at least 2-50 images persecond, at least 1 image per second, at least 12 images per minute or atleast 2 images per minute.

By sampling as frequently as described, the possible movement of thethree-dimensional element and thus of the bodily matter of interest itis possible to track the movement almost in real-time of thethree-dimensional element and hereby of the bodily matter of interest.

Hereby, the possible movements of the body and/or of the element can beused to equalize continuous images by adjusting the images in responseto the possible movement of the three-dimensional element. It islikewise possible during the continuous imaging to adjust the imagingequipment so that the three-dimensional element and thereby the bodilymatter of interest stays in focus of the image. Furthermore, theadjustment of the images may be an adjustment of the position of theimaging equipment, of the couch on which the patient is placed, of thefocal point of the images, and so forth.

Additionally, the possible movements of the body and/or of the elementcan be used to adjust a treatment equipment, e.g. an irradiationequipment, according to the tracking.

Movements to be tracked may be a forced movement, such as a tilting or apartial rotation of the patient during irradiation. The movement mayalso be a voluntary or involuntary movement by the patient. Thevoluntary movement may be the patient moving on the couch or walkingaround in the irradiation room and the involuntary movement may bemovements due to motoric diseases such as Parkinson's Disease orCerebral Palsy.

The three-dimensional element as a marker can be used for collating twoor more diagnostic images used for identification, localisation andgeneration of a therapeutic or surgical scheme generated during theplanning of the therapeutic or surgical specification scheme. Use of thesame three-dimensional element for both performing the therapy orsurgery according to the specification scheme and for collating imagesfor planning of the specification scheme is feasible without any needfor reinsertion or repositioning of the three-dimensional element.

The three-dimensional element as a marker can specifically be used forcollating two or more diagnostic images used for identification,localisation and generation of an irradiation profile generated duringthe planning of radio therapy. Use of the same three-dimensional elementfor both guiding an external beam radio therapy equipment and forcollating images for planning of the radiation therapy is feasiblewithout any need for reinsertion or repositioning of thethree-dimensional element.

According to an aspect of the present invention the three-dimensionalelement may be intended for positioning in an existing natural cavitywithin the human or animal body, without being buried in tissue. Bypositioning the three-dimensional element in an existing natural bodycavity, the risks related to potential tissue damages and the patient'ssensation of the element may be eliminated or at least minimizedcompared to implantable markers being implanted into the patient'stissue.

Additionally, according to an aspect of the present invention insertionof the three-dimensional element may be performed through a naturalopening of the body without at all or at least without substantiallypenetrating any tissue of the body. This way of inserting athree-dimensional element as a marker does not acquire invasive surgery,and thereby the risks related to such surgery is eliminated or at leastminimized compared to implantable markers being inserted by invasion ofskin surfaces and/or tissue.

Furthermore, according to an aspect of the method of the presentinvention a step may be employed of retracting the three-dimensionalelement through a natural opening of the body without at all or at leastwithout substantially penetrating any tissue of the body. By retractingthe three-dimensional element through the natural cavity or opening, theremoval of the three-dimensional element is performed without invasivesurgery and the risks related to such surgery is eliminated or at leastminimized compared to implantable markers being inserted by invasion ofskin surfaces and/or tissue.

The three-dimensional element, when inserted into a natural cavity, istherefore not damaging the surrounding tissue because the cavity is anatural opening of the body. The element is therefore not penetratingany tissue in order to be fastened inside the body. Thethree-dimensional element may be fastened by at least partly abuttingthe inside of the cavity in order for the three-dimensional element notto move inside the cavity.

The three-dimensional element may have different geometrical propertiesdepending on the actual intended position of the three-dimensionalelement in the human or animal body. Additionally or alternatively, thethree-dimensional element may have different physical propertiesdepending on the actual intended use of the three-dimensional element inthe human or animal body, apart from the use as a marker in differentimages. Possibilities of geometrical and physical properties arementioned in the following.

Thus, the three-dimensional element may have a shape allowing passage ofa liquid, gas or solid inside the cavity in which the three-dimensionalelement is positioned. Hereby the natural flow of liquid, gas, or solidinside the cavity is maintained, such as urine in the urethra and bloodin the vein, or such as intestinal gas in the intestines and breath inthe trachea or in the lungs, or such as solid faeces in the intestines,even though a therapy or surgery may cause some swelling of the bodilymatter surrounding the cavity.

The three-dimensional element may be expandable towards the cavity frominside the cavity, when released in the cavity, for fixing thethree-dimensional element in its position at a relative positionaccording to the bodily matter of interest. Likewise, the natural flowof liquid, gas or solid is maintained inside the cavity, such as urinein the urethra and blood in the vein, or such as intestinal gas in theintestines and breath in the trachea or in the lungs, or such as solidfaeces in the intestines, even though the therapy or surgery may causesome swelling of the bodily matter surrounding the cavity.

Furthermore, by expanding the cavity into which the at least oneintegral three-dimensional element is positioned, the three-dimensionalelement is firmly positioned inside the cavity without moving inside thecavity. Any other fastening means such as a barbed shape of thethree-dimensional element is dispensable, and the element is easilyremoved without damaging the inside of the cavity.

The three-dimensional element may have a tubular shape allowing passageof a liquid, gas or solid inside the cavity in which thethree-dimensional element is positioned. A tubular shape will maintainholding the cavity open also during the irradiation and the possibleresulting subsequent swelling.

The three-dimensional element may be a tubular endoluminal prosthesis.The three-dimensional element may therefore already be positioned insidethe body for another purpose such as for expanding a diminished urethraor ureter. The three-dimensional element will maintain holding thecavity open, also during a treatment session and the possible resultingsubsequent swelling caused by the irradiation. The three-dimensionalelement is capable of staying in the cavity during a period of at least30 days and is therefore capable of keeping the cavity open topermeation of liquids, gases or solids all during a treatment sessioneven though the treatment is divided into periods of hours, days orweeks.

In respect of the at least one integral three-dimensional element beinga substantially tubular endoluminal prosthesis, the three-dimensionalelement reduces the need for any additional catheters in order to holdthe cavity in which the three-dimensional element is inserted, open topermeation of liquids, gases or solids.

The at least one integral three-dimensional element may in yet anotheraspect of the present invention be a helical coil of at least one wire.Hereby it is obtained that retraction of the three-dimensional elementis possible through the natural cavity or opening through which it wasinserted by pulling the wire.

The three-dimensional element may have a design enabling insertionand/or retraction of the three-dimensional element with conventionalendoscopic equipment. The three-dimensional element may have acollapsible design, enabling a collapsed design when inserting thethree-dimensional element in a cavity of the human or animal body, andenabling an expanded design when the three-dimensional element has beenpositioned in the cavity of the human or animal body.

In case the three-dimensional element is inserted into a bodily cavity,the cavity may have at least one surrounding wall, and the at least oneintegral three-dimensional element may, according to the invention, havea collapsible design when inserting the three-dimensional element, andsaid three-dimensional element may have a design being expandabletowards the surrounding wall of the cavity, when being released in thecavity. The collapsible design reduces the impact on the inside wall ofthe natural cavity through which the insertion takes place. When beingin the collapsed state, the element may have a substantially linearextension, and when being in the expanded state, the element will changefrom the possibly linear extension to the three-dimensional extension.

An apparatus may be provided in conjunction with the invention, saidapparatus being capable of carrying out the method according to any ofthe aforementioned methods, said apparatus comprising means foridentifying the three-dimensional element, means for establishing apreliminary position of the three-dimensional element and/or atherapeutic or surgical equipment, means for monitoring a possiblemovement of the element and/or means for adjusting the therapeutic orsurgical equipment or the human body or the animal body in response tothe movement.

The means for identifying the three-dimensional element may, in oneaspect, be a computer program for image-detection and means forestablishing a preliminary position of the three-dimensional element mayalso be a computer program for image-detection.

The therapeutic or surgical equipment may be any conventional equipmentfor therapeutic or surgical treatment of bodily matter, such asirradiation equipment for treating a tumor. Means for monitoring apossible movement of the element may be a computer transmitting signalsto the means for adjusting the therapeutic or surgical equipment such asan irradiation equipment or to the means for adjusting the human body orthe animal body in response to the movement.

The three-dimensional element may be made of a biologically compatiblematerial, such as polymers, biological material or metal, such asstainless steel, titanium, platinum, palladium, nickel-titanium andother alloys or combinations of any of these materials. By applying athree-dimensional element of such a biologically compatible material thethree-dimensional element does not cause infection when being in thecavity of the human or animal body.

The three-dimensional element may be made of a shape memory alloy havinga transition temperature with a one-way-memory effect at a temperatureabove body temperature. By applying a shape memory alloy thethree-dimensional element is capable of expanding within the cavity.

In another aspect of the present invention the at least one integralthree-dimensional element may be made of a shape memory alloy having atransition temperature above body temperature, preferably between 37° C.and 50° C. By using shape memory alloy having a transition temperaturebetween 37° C. and 50° C., the surroundings inside the body is notscalded, which otherwise may give rise to an infection or to damagedbodily matter.

Body temperature is construed as the temperature of the body of thehuman or of the animal during the application of the method according tothe invention. In most applications of the method, the body temperatureof a human will be around 37° C.

The body temperature may however differentiate depending on whether itis a human body or an animal body. Some animals have lower normal bodytemperature than humans, and some animals have higher normal bodytemperature than humans.

Also, the body temperature may differentiate depending on the physicalstate of the human or the animal. The temperature may be higher due tofewer if the human or the animal is suffering from illness causingfewer, and the body temperature may be lower due to perhaps unstableblood flow, if the human or animal is newborn or is elderly, or if thehuman or the animal is suffering from illness causing an unstable bloodflow.

By applying a shape memory alloy the three-dimensional element iscapable of expanding within the cavity when heated to the transitiontemperature. Provided the transition temperature is about the normalbody temperature of the human or animal body, the expanding is performedwhen the body has warmed up the element and this expansion of thethree-dimensional element is performed without additional applying ofheat. In the case of a transition temperature in range above the bodytemperature the expanding is obtainable by heating the three-dimensionalelement e.g. by flushing of sterile water or the like fluids, having atemperature above the transition temperature.

Alternatively or additionally, the three-dimensional element may be madeof a material being plastically deformable by hand at a temperaturebelow body temperature, preferably at a temperature below 37° C., morepreferred at a temperature below 20° C. and above 5° C. By using amaterial being plastically deformable by hand the three-dimensionalelement may be easily retracted by the manual force of a physician, andthe three-dimensional element may easily be deformed to a smaller sizeduring the retraction of the three-dimensional element.

Even in the alternative, the three-dimensional element may be made of ashape memory alloy being super elastic at body temperature.

The medical imaging equipment according to the aspect of the inventionmay be any one of the following imaging equipment: Magnetic Resonancescan (MR-scan), Nuclear Magnetic Resonance scan (NMR-scan), MagneticResonance Image scan (MRI-scan), Computerized Tomography scan (CT-scan),Cone Beam CT-scan, Positron Emission Tomography (PET), Single PositronEmission Computed Tomography (SPECT), Single Positron EmissionTomography (SPET), Image-Guided-Radiation-Therapy (IGRT,Ultrasound-scan, or X-ray, high-energy photons equipment or high voltageequipment.

The image may, according to the invention, be derived and processed byutilizing energy of an irradiation source for treatment. Thereby use ofother equipment is no longer necessary and a substantial amount of costand space in the irradiation room is saved.

In an additional aspect of the invention, the image may be derived andprocessed by utilizing energy of the treatment irradiation beam. Thus,use of other equipment is no longer necessary and a substantial amountof cost and space in the irradiation room is saved.

Medical marker elements may be delivered to a target bodily matter suchas a body organ or a body tissue via a marker element delivery system.The marker element delivery system may be an elongated device that isbrought through to body vessels or other body cavities or in proximityto target organs or tissue. Once the marker element is in position, themarker element delivery system is retracted, while the marker elementstays in place. The marker element delivery system may be speciallydesigned depending different parameters such as the shape of the markerelement and/or the body organ and/or the body tissue or the body cavity,into which the marker is to positioned and/or on a possible body openingthrough which the marker element delivery system is to be inserted andretracted. Use of such marker element delivery system allows medicalpersonnel to perform marker positioning in a fast and non-invasivemanner.

Possible applications where collating of two or more diagnostic imageswith a three-dimensional marker could be advantageous are the followingnon-exhaustive applications:

-   -   Planning of external radio therapy treatment, i.e. by a beam        apparatus or other medical applications where there is an effect        of some bodily matter such as tissue and/or a body part being        easier to detect in one type of images than in another type of        image.    -   Planning of internal radio therapy treatment including        brachytherapy or other medical applications where there is an        effect of some bodily matter such as tissue and/or body parts        being easier to detect in one type of images than in another        type of image.    -   Follow-up on anatomic changes on a patient's anatomy, e.g.        growth or shrinking of a certain bodily matter such as a tissue        of interest, e.g. a cancer tumor or other foreign body, or such        as a bodily organ of interest, e.g. the liver or other more or        less vital body organs, or such as bodily parameters e.g. nerve        impulses from certain parts of the brain.    -   Follow-up during treatment, surgery or diagnosis of e.g.        internal movement of certain bodily matter such as a tissue of        interest, e.g. a cancer tumor or other foreign body, or such as        a bodily organ of interest, e.g. the liver or other more or less        vital body organ, or such as a bodily parameter of interest,        e.g. nerve impulses to and form certain part of the brain.    -   Investigation of respiratory movement and/or rhythm, e.g. for        the use of possible gating of a treatment session.    -   Guidance of external treatment equipment, e.g. an irradiation        equipment, by tracking of internal body organ movements and/or        correction of inaccuracies due to set-up differences, when        obtaining the images.

The method according to the invention may be used in conjunction with amethod for guiding a treatment equipment located outside a human body oroutside an animal body. In the following an external beam radio therapyequipment is used as an example. The method could, however, be used forother types of treatment equipments. Said method of guiding comprisingthe steps of:

-   -   identifying, in an image, at least one integral        three-dimensional element visible in the image, said at least        one integral three-dimensional element being in position in a        cavity of the human body or the animal body,    -   establishing, in the image, a preliminary position of the at        least one integral three-dimensional element visible in the        image in relation to a reference,    -   establishing a preliminary position of the irradiation equipment        in relation to the reference,    -   adjusting the irradiation equipment in relation to the reference        in response to the position of the at least one integral        three-dimensional element in relation to the reference.

During the step of identifying, in an image, at least one integralthree-dimensional element visible in the image, the at least oneintegral three-dimensional element is in position. Prior to identifying,in an image, at least one integral three-dimensional element visible inthe image, an additional step may be inserting the at least one integralthree-dimensional element into a cavity of the human body or the animalbody.

By identifying the position of the at least one integralthree-dimensional element in relation to the position of the disorderedtissue, the position of the disordered tissue may then be establishedbased on establishing the position of the three-dimensional element.This is advantageous due to the fact that the disordered tissue is notidentifiable in all kinds of images, in which the three-dimensionalelement is identifiable. By being able to establish the position of thethree-dimensional element in a two dimensional image, the exact positionof the disordered tissue may be established due to the fact that theelement and the disordered tissue moves simultaneously in relation tothe human or animal body.

The dimensions of the three-dimensional element are known in advance andbased on the two-dimensional image of the three-dimensional element thedimensions give an exact knowledge of how the three-dimensional elementis positioned inside the body and perhaps is being rotated inside thebody. By knowing the dimensions of the three-dimensional element inadvance and by being able to detect the dimensions in an image, theexact position of the three-dimensional element inside the body may becalculated. The knowledge about the position of the three-dimensionalelement established in the image gives an exact knowledge of where thedisordered tissue is positioned, because the disordered tissue and thethree-dimensional element have been found to have a substantially fixedrelationship and any possible movement of the disordered tissue resultsin corresponding movement of the three-dimensional element and viceversa.

Hereby, positioning of the disordered tissue may be performed accuratelybased on the position of the element even though the patient has beenmoved between the examination room and the irradiation room or has movedjust before setting up the patient and the treatment equipment forirradiation. It is likewise possible during the irradiation of thepatient to adjust the equipment so that the element and thereby thedisordered tissue, such as a tumor, of the patient stays in focus of theirradiation equipment.

By being able to adjust the irradiation equipment based on the element,the irradiation may be performed more precisely and the adjusting of theirradiation equipment may be done automatically by a computer.

Additionally, by being able to irradiate more precisely, it is possibleto subject the patient to a higher total dose of irradiation withoutdamaging tissue surrounding the disordered tissue and as a result it ispossible to subject the patient to irradiation more times with the samerefractory doses in order to more effectively eliminate the disorderedtissue, or to subject the patient to irradiation fewer times with higherrefractory doses in to more effectively eliminate the disordered tissue,without damaging healthy tissue.

Additionally, the method according to the present invention may furtherbe used in conjunction with a method for adjusting an irradiationequipment located outside a human body or outside an animal body, saidmethod comprising the steps of:

-   -   monitoring a possible movement of the three-dimensional element        in relation to the irradiation equipment,    -   adjusting the irradiation equipment in response to the possible        movement of the three-dimensional element.

Hereby, the aforementioned inaccuracies are increasingly diminished inthat the possible movements of the body and/or of the element isequalized by adjusting the irradiation equipment in response to thepossible movement of the at least one integral three-dimensionalelement. It is likewise possible during the irradiation to adjust theequipment so that the three-dimensional element and thereby thedisordered tissue, such as a tumor, of the patient stays in focus of theirradiation equipment. Furthermore, the adjustment of the irradiationequipment may be an adjustment of the position of the irradiationequipment, of the couch on which the patient is placed, of the power ofthe irradiation source, of the focal point of the beam, of the intensityof the irradiation beam, of movement of plates or a shield changing theshape of the irradiation beam, and so forth.

Additionally, the adjusting of the irradiation equipment may furthermorebe a deflection or a focusing of the irradiation beam in relation to anymovements during irradiation. Such movement may be a forced movement,such as a tilting or a partial rotation of the patient duringirradiation. The movement may also be a voluntary or involuntarymovement by the patient. The voluntary movement may be the patientmoving on the couch or walking around in the irradiation room and theinvoluntary movement may be movements due to motoric diseases such asParkinson's Disease or Cerebral Palsy.

The advantages of being able to adjust the irradiation equipment duringirradiation reside in the possibility of irradiating the body fromdifferent angles. Thereby, the disadvantage of irradiating possiblyhealthy tissue surrounding the disordered tissue is minimized.Furthermore, the adjustment may be performed so that irradiation ofcertain critical healthy tissue is avoided. The adjustment of theirradiation equipment may also be a limitation of the total dose ofirradiation from a certain angle in order to avoid exceeding theirradiation limit of healthy tissue being irradiated from that certainangle.

The steps of identifying, establishing, monitoring and adjusting may bedone automatically, and the monitoring step may be executed at anappropriate frequency, such as once every 3 seconds or less depending onthe equipment available.

According to the present invention in general, and not only related toguiding of irradiation equipment, different aspects and advantages aredisclosed in the following:

In one aspect, a reference may be a previous image of thethree-dimensional element having been inserted into the cavity of thebody. Such a previous image may conveniently be the image in which thebodily matter of interest, such as a tumor, was detected and theposition and/or shape of the bodily matter of interest were establishedduring a pre-examination of the patient.

In another aspect, the previous image of the at least one integralthree-dimensional element may also be the last image derived of thethree-dimensional element or the image derived for setting up thepatient before therapy or surgery.

Additionally, according to an aspect of the present invention insertionof the three-dimensional element may be performed through a naturalopening of the body without at all or at least without substantiallypenetrating any tissue of the body. This way of inserting athree-dimensional element as a marker does not acquire invasive surgery,and thereby the risks related to such surgery is eliminated or at leastminimized.

Furthermore, according to an aspect of the method of the presentinvention a step may be employed of retracting the three-dimensionalelement through a natural opening of the body without at all or at leastwithout substantially penetrating any tissue of the body. By retractingthe three-dimensional element through the natural cavity or opening, theremoval of the three-dimensional element is performed without invasivesurgery and the risks of contamination related to such surgery iseliminated or at least minimized.

The three-dimensional element, when inserted into a natural cavity, istherefore not damaging the surrounding tissue because the cavity is anatural opening of the body. The element is therefore not penetratingany tissue in order to be fastened inside the body. Thethree-dimensional element is fastened by at least partly abutting theinside of the cavity in order for the three-dimensional element not tomove inside the cavity.

Advantageously, when the invention is used in conjunction with a methodfor adjusting a therapeutic or surgical equipment such as an irradiationequipment located outside a human body or outside an animal body,monitoring and adjusting of the therapeutic or surgical equipment suchas the irradiation equipment may be performed during therapeutic orsurgical treatment such as irradiation of the bodily matter, e.g. adisordered tissue such as the tumor.

In another aspect of the present invention the at least one integralthree-dimensional element may be a substantially tubular endoluminalprosthesis.

Additionally, possible monitoring of the movement of the at least oneintegral three-dimensional element may according to the presentinvention be performed by producing up to 50 images per second, at least2-50 images per second, at least 1 image per second, at least 12 imagesper minute or at least 2 images per minute depending on the medicalimaging equipment, at least 2-50 images per second, at least 1 image persecond, at least 12 images per minute or at least 2 images per minute.

By sampling as frequently as described, the possible movement of thethree-dimensional element and thus of the disordered tissue may beequalized almost instantly and the method is performed almostcontinuously, whereby the aforementioned damage of healthy tissue can besubstantially decreased.

According to the present invention, each individual image may be a twodimensional projection image or a three-dimensional image, and whereinthe image is derived and processed by medical imaging equipment.

Furthermore, when the invention is used in conjunction with a method foradjusting an irradiation equipment located outside a human body oroutside an animal body, the patient is not unnecessarily irradiated.When the dose of irradiation is calculated, the irradiation of thepatient, in order to produce images to establish the extension of thedisordered tissue, such as a tumor, is included. The dose is calculatedso that the surrounding healthy tissue is not un-recoverably damaged.The irradiation of the patient is thereby used in order to treat thepatient in the correct area and not just for producing examinationimages.

By using the same equipment as for irradiation of a disordered tissue,time is saved for changing equipment back and forth when an image has tobe derived.

When the invention is used in conjunction with a method for adjusting anirradiation equipment located outside a human body or outside an animalbody, the image may be derived and processed by utilizing electricenergy from an energy source for producing electric power for theirradiation source.

The at least one integral three-dimensional element may have a designenabling insertion and/or retraction of the three-dimensional elementwith conventional endoscopic equipment. By being able to useconventional endoscopic equipment during insertion and/or retraction ofthe three-dimensional element, costs of additional equipment is savedand the time in changing between utilizations of different equipmentduring the insertion or retraction of the three-dimensional element isdecreased.

In case the three-dimensional element is inserted into a bodily cavity,the cavity may have at least one surrounding wall, and the at least oneintegral three-dimensional element may, according to the invention, havea collapsible design when inserting the three-dimensional element, andsaid three-dimensional element may have a design being expandabletowards the surrounding wall of the cavity, when being released in thecavity. The collapsible design reduces the impact on the inside wall ofthe natural cavity through which the insertion takes place. When beingin the collapsed state, the element may have a substantially linearextension, and when being in the expanded state, the element will changefrom the possibly linear extension to the three-dimensional extension.

An apparatus may be provided in conjunction with the invention, saidapparatus being capable of carrying out the method according to any ofthe aforementioned methods, said apparatus comprising means foridentifying the three-dimensional element, means for establishing apreliminary position of the three-dimensional element and a therapeuticor surgical equipment, means for monitoring a possible movement of theelement and means for adjusting the therapeutic or surgical equipment orthe human body or the animal body in response to the movement.

The means for identifying the three-dimensional element may, in oneaspect, be a computer program for image-detection and means forestablishing a preliminary position of the three-dimensional element mayalso be a computer program for image-detection.

The therapeutic or surgical equipment may be any conventional equipmentfor therapeutic or surgical treatment of bodily matter, such asirradiation equipment for treating a tumor. Means for monitoring apossible movement of the element may be a computer transmitting signalsto the means for adjusting the therapeutic or surgical equipment such asan irradiation equipment or the human body or the animal body inresponse to the movement.

Medical marker elements may delivered to a target bodily matter such asa body organ or a body tissue via a marker element delivery system. Themarker element delivery system may be an elongated device that isbrought through to body vessels or other body cavities or in proximityto target organs or tissue. Once the marker element is in position, themarker element delivery system is retracted, while the marker elementstays in place. The marker element delivery system may be speciallydesigned depending different parameters such as the shape of the markerelement and/or the body organ and/or the body tissue or the body cavity,into which the marker is to positioned and/or on a possible body openingthrough which the marker element delivery system is to be inserted andretracted. Use of such marker element delivery system allows medicalpersonnel to perform marker positioning in a fast and non-invasivemanner.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be described with referenceto the accompanying drawings, in which:

FIG. 1 shows a prior art marker being inserted by surgery through thetissue of a human body,

FIG. 2 shows three prior art markers which have been inserted into thetissue surrounding a tumor,

FIG. 3 shows a human body lying on a couch below a therapeutic orsurgical equipment, in the embodiment shown an irradiation equipment,

FIG. 4 shows a three-dimensional element having been inserted into thenatural cavity a urethra of a male,

FIG. 5 shows an X-ray image of a three-dimensional element as shown inFIG. 4,

FIG. 6 shows an X-ray image of another three-dimensional element,

FIG. 7 shows a three-dimensional element having been inserted into thenatural cavity a urethra of a male,

FIG. 8 shows an example of a three-dimensional element,

FIGS. 9, 10 and 11 show other examples of a three-dimensional element,

FIGS. 12 and 13 show an example of three-dimensional element in an imagederived from a mega voltage equipment, and

FIG. 14 shows an amalgamation of images having the three-dimensionalelement in the center and derived by CT-scan.

The drawings are schematically and shown for the purpose ofillustration.

FIG. 1 shows the insertion of prior art markers m through the skin byuse of invasive surgery, the insertion being done in order to locate thedisordered tissue d, such as a tumor, in an image derived forpositioning the irradiation of the tumor d. When inserted as shown inFIG. 2, the three or more markers m are positioned in relation to theirradiation equipment, and the irradiation source is turned on for aperiod of time. Subsequently to the time period of irradiation, theirradiation is interrupted. The irradiation of the tumor d may becontinued when a period of at least a few days has lapsed so that thesurrounding healthy tissue may withstand a new irradiation. During thetime period of irradiation, the irradiation equipment is at no timeadjusted in order to compensate for any movement of the tumor duringthis irradiation.

The prior art markers in shown FIGS. 1 and 2 may move considerablywithin the body between two irradiation periods in which case moremarkers may have to be inserted.

DESCRIPTION OF THE PRESENT INVENTION

Given a possibility to collate, align and compare different images moreexactly than by the prior art methods, facilitates the possibility tocombine different images, being derived by different imaging equipments,possibly being derived by different imaging modalities, and to track adevelopment over time, within images obtained at different times.Combination of images being derived by different imaging equipments,possibly being derived by different imaging modalities, facilitatesimproved identification of a bodily matter of interest, e.g.identification of a cancerous tissue to be irradiated with an externalbeam radio therapy equipment. Tracking a development over time, withinimages obtained at different times, facilitates tracking of movementand/or growth/shrinking of bodily matter for better diagnosis, e.g.tracking of the growth of a cancerous tumor or tracking of the movementof a cancerous tumor according to the patient's breathing cycle.

In the following description of the invention, identification of acancerous tumor, planning of the specifications of the irradiationtreatment to be delivered to the cancerous tumor, and, tracking amovement of the cancerous tumor will be used as one of several examples,where the present invention may be employed.

Possible other use applications in relation to collating images by themethod according to the invention may be the following non-exhaustivelist of applications:

-   -   Reduction of inaccuracies due to set-up differences between the        images. In one example such as therapy by irradiation,        inaccuracies may result in difficulties in only radiating the        target tissue or in difficulties in controlling the intensity of        irradiation. In an example of diagnosis, inaccuracies may result        in difficulties in performing a medically safe diagnosis or in        performing a sufficiently fast diagnosis. In an example of        surgery, inaccuracies may result in difficulties in performing        complicated surgery or in performing surgery within a narrow        space.    -   Identification of unwanted in-body elements, e.g. position and        size of cancer tumors, position and size of encrustations or        stone-formations, position and size of foreign bodies.    -   Planning of treatment and/or identification of treatment target,        e.g. planning of irradiation treatment, or identification of        treatment target during diagnosis, or planning of surgery        process during a surgery based on perhaps different images from        different angles.    -   Identification and/or diagnosis of orthopaedic damages (bone        fractures, joint fractures or joint dislocations), e.g.        identification of small bone fractures within the body, or        diagnosis of correct treatment of fractures or dislocations of        physically complicated joints.    -   Identification of possible obstructions of bodily lumens, e.g.        urothelial obstructions due to encrustation or foreign bodies,        cardiovascular obstructions due to encrustation, etc.

Possible use applications in relation to comparing images by a methodaccording to the invention may be the following non-exhaustive list ofapplications:

-   -   Tracking of growth or shrinkage of a bodily matter such as        tracking non-wanted growth of cancerous tumor or tracking of        intended shrinkage of a cancerous tumor during irradiation        therapy, or tracking of non-wanted further shrinkage of        cirrhosis of the liver, or tracking of intended growth of        internal body organs such as a treated cirrhosis of the liver.    -   Tracking of growth or shrinkage of a cardiovascular lumen such        as tracking of non-wanted stenosis shrinkage of blood vessels or        tracking of intended growth of a stenosis of a blood vessel        during therapy, or tracking of non-wanted further shrinkage of        urethra, or tracking of intended growth of ventricles of the        heart or volume of the lungs.    -   Tracking movement of a foreign body, a parasite or the like such        as tracking of non-wanted biliary calculus or tracking or        tracking of intestinal parasites like worms.    -   Correction of inaccuracies due to set-up differences between        obtaining the reference image and obtaining the present image        such as inaccuracies occurring between different times of        treatment, where an outside element such as a patient bed is        used as reference or such as inaccuracies occurring between on        reference image of a first imaging equipment and another        reference image of a second imaging equipment.    -   Correction of inaccuracies due to internal body organ movements        between obtaining the reference image and obtaining the present        image such as internal body organs moving during inhalation and        exhalation or such as internal body organs having moved between        one point of time imaging the body organ and a later point of        time imaging the body organ.

In the following description of the invention, identification of acancerous tumor, planning of the specifications of the irradiationtreatment to be delivered to the cancerous tumor, and, tracking amovement of the cancerous tumor will be used as one of several examples,where the present invention may be employed. In the following, planningof irradiation treatment will be used as one example among all theexamples mentioned above and among further examples of application,which the skilled person may envisage as applications of the methodaccording to the invention.

In the following, a tumor 6 will be used as an example of disorderedtissue. However, other types of disordered tissue, other than tumors,may also be treated during guiding of the irradiation equipment whenemploying an equipment guidance method as described. Also, other bodilymatters of interest than disordered tissue may be subject to treatmentby therapy or surgery during operation of therapeutic or surgicalequipment when employing an equipment operating method, such as theirradiation guiding as described.

As mentioned, in the following, the invention will be described withreference to a cancerous tumor as example of bodily matter of interest.However, as previously mentioned, in the context of the presentinvention, bodily matter is to be construed as any matter relating tothe body, e.g. body organs such as the prostate, body tissue such as atumor or body substances such as urine, etc. Also, the invention is notlimited to bodily matter, but may also be applied in relation to bodilyparameters. As previously mentioned, in the context of the presentinvention, bodily parameters are to be construed as any parameterrelated to the body, e.g. physiologic parameters such temperature,bodily fluid parameters such as urine flow, bodily electrochemicalparameters such as nerve impulses, etc.

Furthermore, as mentioned, in the following, the invention will bedescribed with reference to irradiation and irradiation equipment asexample of a method and an equipment of treatment. However, aspreviously mentioned, in the context of the present invention, treatmentmay also be other types of therapeutic treatment or may be surgicaltreatment, such as therapeutic treatment by brachy therapy, treatment ofblood vessels or other vessels for the flow of bodily gas, liquid orsolids etc. Possible types of surgical treatment may be insertion ofirradiating agents for use in brachy therapy, insertions of surgicalequipment for biopsy, insertion of surgical equipment for fertilisationtreatment, guiding of surgical equipment during a surgery in any partsof the body etc.

Accordingly, the specific example of a cancerous tumor as a bodilymatter of interest, and the specific example of irradiation as a methodof treatment by therapy or surgery, and the specific example ofirradiation equipment as an equipment for treatment by therapy orsurgery is not to be construed as limiting the scope of protectionaccording to the claims.

When a patient 1 has been given the diagnosis of having cancer, thecancer is often positioned inside the body of the patient in the form ofdisordered bodily matter, namely disordered tissue 6, such as a tumor 6,as shown in FIG. 3. The disordered tissue may result in a disorderedorgan such as the prostate. If the patient is intended for havingtreatment by irradiation therapy, a step of planning the specificationsof the irradiation to be delivered is often performed. The planning ofthe specifications of the irradiation to be given is often based onimages depicting the bodily matter within and around the canceroustumor.

One important part of planning the specifications of the irradiation tobe given is to define the form of the target for the irradiation to bedelivered. The target of the irradiation profile to be delivered willoften contain both the tissue being identified as the cancerous tumor,and a margin surrounding the tissue being identified as the canceroustumor, applied to compensate for any inaccuracies in the identificationof the cancerous tumor in the planning images, and to compensate for anyinaccuracies in the actual delivery of the irradiation treatment, e.g.any inaccuracies involved in positioning an irradiation equipment and apatient exactly as planned before starting a treatment session.

Any limitation of the inaccuracies in the identification of thecancerous tumor and any limitation of the inaccuracies involved in exactpositioning of the irradiation equipment and/or of the patientfacilitates a possibility to decrease the margin for compensation ofthese inaccuracies, and hereby such limitations of the inaccuracies mayfacilitate improved treatment with the potential of less side effectsfor the patient.

The image 4 for planning of the specifications of the irradiation to begiven is investigated, and the tumor 6 is located in the image 4 beforethe actual treatment of the patient 1. A series of images 4 may bederived in order to establish the extension of the tumor 6. In oneaspect of the present invention, the position of the three-dimensionalelement 7 is determined by producing a series of images 4 using as anexample MR-scanning techniques or X-ray CT-scanning techniques. Whenestablishing the extent of the tumor and if no element is alreadypositioned in the body of the patient 1, a three-dimensional element 7,being suitable as a marker of the tumor 6, is inserted into the patient1 before obtaining the images. In other situations, when establishingthe extent of the tumor, an element, being suitable as a marker of thetumor 6, is already positioned in the body of the patient 1. Thethree-dimensional element is inserted or is in position within a certaindistance from the tumor 6 to be treated or inside the volume to betreated. When irradiating a tumor 6 inside the prostate, thethree-dimensional element 7 is often positioned inside the prostaticurethra and is therefore in immediate vicinity of the area 6 to betreated as shown in FIGS. 4, 5, 6, 7, 12, 13 and 14.

When having the three-dimensional element inserted in the patient, in aposition within the cancerous tumor, or in a position near the canceroustumor, and the three-dimensional element is known to be located andfixed in a position within the patient's body which moves in a mutualrelationship with the cancer tumor, the three-dimensional element can beused for collating multiple diagnostic images intended for identifyingthe treatment target, and for planning the specifications of theirradiation.

Some imaging types are known to provide different information ofdifferent types of bodily matter. Therefore some tissue material (e.g.the cancerous tissue) may be easier to detect in a MR-image, but othercrucial information about the surrounding bodily matter may be easier todetect in an X-ray CT-image, and vice versa. Therefore an improved planof the specifications for the irradiation may be generated based on afusion of images from different imaging types, e.g. by collatingMR-images and X-ray CT-images.

A known problem resulting from the prior art methods is however, that anexact alignment of the different types of images is often very difficultto generate, since the set-up conditions of the imaging equipmentsand/or the patient is not exactly identical when obtaining the differentimages. Furthermore it may be difficult to clearly detect identicalpoints, lines, areas or volumes in all the different images, due to thedifferent quality and characteristics of the different imaging types.

With the three-dimensional element inserted in the patient prior toobtaining the images, the three-dimensional element, with itscharacteristics of being clearly detectable in all types of images, canbe used as a marker for alignment of the coordinate systems of theindividual images, so that the different images are accurately alignedaccording to the three-dimensional element, possibly in threedimensions. Since the three-dimensional element is known to bepositioned and fixed in a position within the patient's body in a mutualrelationship with the bodily matter of interest, an alignment of thethree-dimensional element in the images will also result in an alignmentof the bodily matter of interest in the images.

The collation of the images based on the three-dimensional element willbe accurate even though the images are obtained under different set-upconditions of the imaging equipments and/or of the patient, and eventhough the images might be obtained with a time interval between theobtaining of the images, and even though the images may have differentpicture quality.

The collation of the images used for planning the specifications of theirradiation may be performed automatically, guided by a computer, basedon the known geometry of the three-dimensional element.

In one aspect of the present invention, the pre-treatment planningimages may be stored as a reference for the later irradiation session.In the pre-treatment planning images the position of thethree-dimensional element 7 is identified, and the position of thethree-dimensional element relative to the cancerous tumor is stored forlater referencing during the actual irradiation session. A referenceposition within the pre-treatment images could be set for example as apoint in the middle of the three-dimensional element 7.

When starting the actual irradiation treatment session the irradiationequipment and/or the patient may be guided to its intended position,according to the plan of the specifications for the irradiation, byobtaining a new image of any imaging type, and based on a collation ofthis image and the pre-treatment planning images, based on the positionof the three-dimensional element. When collating thisjust-before-treatment-image and the pre-treatment planning images theinformation about the difference between the position and the differencebetween the rotation of the three-dimensional in thejust-before-treatment-image and the pre-treatment planning images givesthe information needed to compensate for inaccuracies in the set-up ofthe irradiation equipment and/or the patient's position.

By deriving additional images during the actual irradiation session asimilar guiding of the irradiation equipment and/or the patient'sposition may be performed during the actual irradiation session, basedon the collation of the images according to the position of thethree-dimensional element in each individual image. Hereby it becomespossible to compensate for any movements of the irradiation equipment orthe patient or internal organ movements within the patient's body, etc.that may occur during the actual irradiation process. If the frequencyof obtaining the additional images is high, and a rapid automaticcollation of the images is performed, an almost continuous guiding ofthe treatment is possible. This facilitates for example guidance of theirradiation according to a movement of the cancerous tumor, due tointernal organ movements resulting from respiratory movement of thelung.

The following description describes in more details a possible methodfor guiding an external beam radio therapy equipment according to thepresent invention.

The position of the three-dimensional element 7 may be determined byproducing a series of images 4. The images 4 are entered into thecomputer. The computer calculates and saves the mutual relationshipbetween the three-dimensional element 7 and the tumor. The mutualrelationship has been derived by establishing a distance between thetumor 6 and the three-dimensional element 7, which distance is fixedduring any kinds of movements of tissue inside the body in relation tofor example the bone structure or movements of the body 1 as a whole. Bythe wording a fixed distance is meant that the tumor 6 and thethree-dimensional element 7 have substantially no relative movement inrelation to one another.

Establishing a preliminary position of the three-dimensional element 7in the image 4 in relation to a reference may, according to theinvention, be performed by identifying a known geometrical shape, suchas the pitch distance between the windings of a coil shaped element 7,the bending in a structural transition of the three-dimensional element7, a circumference or contour of the three-dimensional element 7, etc.

Subsequently, a preliminary position of the irradiation equipment 2 isautomatically established by a computer. Establishing a preliminaryposition of the irradiation equipment 2 in relation to the reference maybe performed by measuring the distance from the position, whereradiation is emitted from the irradiation equipment and to startingpoint/set-up point in the image 4, including identifying a level inwhich the plane of the image 4 is positioned. Establishing of apreliminary position of the irradiation equipment in relation to thereference may also be performed by identifying where a certain bonestructure in the body is positioned in relation to the irradiation heador it may be performed by establishing the mutual relationship betweenthe couch and the position where the radiation is emitted form theirradiation equipment.

During the period of time in which the irradiation equipment 2 isactivated in order to irradiate the tumor 6, any possible displacementof the element 7 is monitored. Provided a possible movement is beingdetected the irradiation equipment 2 is adjusted in response to themovement of the element so that the irradiation of the tumor 6 isexecuted as precisely as possible.

In this regard, the irradiation equipment 2 comprises, among otherfeatures, the couch where the patient may lie or sit, the irradiationsource, the irradiation beam, and plates or shield defining the shape ofthe beam.

Adjusting the irradiation equipment 2 may therefore be an adjustment ofthe position of the irradiation equipment 2, an adjustment of theposition of the couch 5 in relation to the equipment 2, an adjustment ofthe power of the irradiation source, an adjustment of the focal point ofthe beam 3, an adjustment of the intensity of the beam 3, an adjustmentof movement of the plates or the shield in order of changing the shapeof the beam 3 and so forth. The adjusting of the irradiation equipment 2may furthermore be a deflection of the irradiation beam 3 in relation toa body to be irradiated.

The adjustment of the irradiation equipment 2 may also be to turn downthe power of the irradiation source, when the element 7 is monitored tobe outside a certain area, and to turn on the power again, when theelement 7 is within the certain area again. It may furthermore bepossible to adjust the irradiation power during the irradiation period,in order to subject some areas of the tumor 6, to higher dose ofirradiation than other areas, e.g. subjecting the irradiation marginarea to smaller dose of irradiation than the tumor 6 itself, orsubjecting some very critical areas in the human or animal body tosmaller dose of irradiation than the tumor 6 itself.

Instead of turning on or turning down the power, the irradiation beammay be deflected or the focal point of the irradiation beam may bechanged. By irradiating the whole area of the tumor 6 it may benecessary to irradiate the tumor 6 by moving the irradiation beam in apredefined movement pattern.

Monitoring a possible movement of the three-dimensional element 7 inrelation to the irradiation equipment 2 may be performed in pre-selectedintervals such as 10-20 times a second, such as 1-2 per minute, etc.depending on the medical imaging equipment and based on the expectedfrequency of movement of the three-dimensional element 7.

When planning irradiation of the patient, an irradiation margin is usedin order to be certain that the tumor 6 is irradiated sufficiently, eventhough the step of monitoring and of adjusting provides for a decreaseof the size of the irradiation margin.

Before performing the actual irradiation, the three-dimensional element7 having been positioned in relation to the tumor 6 is located when thepatient is lying on the irradiation couch or when the patient in anyother way is located in the irradiation room. The location of thethree-dimensional element 7 may in one embodiment be established byderiving a high-voltage image 4 using the irradiation equipment 2itself. The patient or the irradiation equipment 2 is positioned so thatthe three-dimensional element 7 is positioned as previously planned, andso that the reference is centered in the middle of the three-dimensionalelement 7. Hereby a starting point is established also called thepreliminary position of the irradiation equipment 2 and of the element 7in relation to the reference.

The reference may in this aspect be any previous image 4 derivedidentifying the tumor 6 in relation to the three-dimensional element 7.The previous image 4 may also be the last image 4 derived in order tomonitor a possible movement of the three-dimensional element 7, or thereference may be an image 4 derived during the pre-examination. By theprevious image 4 is meant an image 4 derived before the present image 4,in which previous image 4 the position of the three-dimensional element7 has been established.

In another aspect, the reference may be the couch on which the patientis located during the irradiation or the reference may be theirradiation equipment 2 itself. The reference may also be a certain bonestructure or another identifiable structure inside or outside the humanor animal body.

By automatically monitoring and detecting a possible movement of thethree-dimensional element 7, the method is capable of adjusting theirradiation equipment 2 or the patient in relation to each other everytime the three-dimensional element 7 is moving from the establishedpreliminary position. It is hereby obtained to compensate for frequentmovement of the tumor caused for example by respiration or smallmovements made by the patient, said movements being made by force, beingmade voluntary by the patient or being made involuntary by the patient.A considerable improvement of the accuracy of the irradiation isaccomplished and the irradiation of healthy tissue is reduced.

FIG. 14 shows that merging different images 4 together based on a centerof the images being positioned within boundaries of thethree-dimensional element 7 gives a very accurate localization of thetissue of interest, for example the prostate.

By sampling images 4 during the irradiation of the tumor the monitoringof any possible movement of the three-dimensional element 7 and thus ofthe tumor 6 may be equalized momentarily all most the instance themovement appears. The sampling frequency may vary from ten images persecond or faster to one image per three second depending on theequipment used for producing the images 4.

High voltage equipment such as the irradiation equipment 2 itself has asampling frequency (or sampling rate) less than for example MR-scanningequipment. However, when using the irradiation equipment 2 itself theother equipment is dispensable.

Often, X-ray is used to establish the first image 4 for localization ofthe tumor 6 in relation to the three-dimensional element 7, but otherequipment such as CT-scanning equipment and MR-scanning equipment may beused likewise. The position of the tumor 6 in relation to thethree-dimensional element 7 is thus determined prior to the patiententering the irradiation room.

In one aspect of the present invention the patient itself inputs thefirst image 4 into the computer of the irradiation equipment, said firstimage 4 being relied upon as the previous image 4 and thereby as thereference in the computer of the irradiation equipment 2. Subsequently,the computer controls the irradiation equipment 2 for producing an image4 for establishing the position of the element 7 in relation to theirradiation equipment 2. Then the computer adjusts the irradiationequipment 2 if necessary in relation to the position of the element 7and the irradiation of the human or animal body begins.

The three-dimensional element 7 may be all kinds of objects provided inthe body for a number of other reasons. Such objects may be all kinds ofendoluminal prosthesis often being tubular, such as a element 7 placedin the urethra and other natural cavities, such as the urological tract,the urethra, the biliary tract, the airways, the intestine, or the bloodvessels in the human body.

If an element 7 is already present in the vicinity of the tumor to beirradiated, the element 7 will secure the passage of the liquid, gas orsolid inside that natural cavity, as mentioned above. It is well knownthat the tissue having been irradiated becomes distended and thereby maycause a reduction of the volume of the natural cavities. Athree-dimensional element 7, such as a tubular endoluminal prosthesiscan help to counteract this reduction of the volume of the cavity.

For the reason of avoiding a reduction of the volume of the naturalcavities one or more elements 7 may be provided which may be used inguiding the irradiation equipment 2 in order to adjust for theaforementioned momentary movements during the irradiation.

Furthermore the three-dimensional element 7 may in another aspect of thepresent invention have a shape enabling insertion and retraction in anatural cavity. Additionally, when inserted into the cavity a part ofthe element 7 may expand in order to provide a force against thesurrounding wall of the cavity so as to fasten the element 7 in thisposition. In other embodiments of the present invention the fastening ofthe element 7 in relation to the surrounding walls of the cavities maybe done by at least a part of the element 7 being attached at leastpartly to tissue outside the natural cavity or by the element 7 havingan Y-shape, an I-shape or the like shapes processing a locking mechanismblocking movements in the longitudinal direction of the cavity, such asthe ureter, vein or the like cavity.

An example of such a three-dimensional element 7 according to thepresent invention is a tubular stent used for insertion into the urethrain the vicinity of the prostate as shown in FIGS. 4, 5, 7 and 8. Whenthe stent has been positioned in the part of the male urethra passingthrough the prostate and expansion of the end of the element 7 closestto the external urethral sphincter has occurred, the element 7 willremain in position and allow urinary passage without obstructing thefunction of the sphincter.

The wire design of the element 7 is of particular advantage when theelement 7 is to be removed or retracted from a body cavity because theelement 7 of a shape memory alloy becomes soft when it is cooled. Theelement 7 may be removed by grasping in any part of the helically woundwire and subsequently pulling the coil out of the cavity as a wire.Furthermore, the element 7 may have a different design than a coiledwire and the element may be made of other alloys so when cooled theelement 7 becomes super elastic and is retractable by folding up theelement 7 before retraction.

A further advantage of using a three-dimensional element 7 with a kindof locking mechanism is that the element 7 will move together with thetumor 6 during respiration or other partly movements of the human oranimal body or during total movement of the same body as shown in FIG.7. Due to the fact that the element 7 moves with substantially norelative movement in relation to the tumor 6, the irradiation equipment2 may be adjusted in relation to the possible movement of thethree-dimensional element 7 in order to accurately irradiate the tumor6. In an image 4 produced by the irradiation equipment 2 the computer isnot able to detect the tumor 6 since it is not visible in such image 4.However, a three-dimensional element 7 made of metal, such as stainlesssteel, titanium, platinum, palladium, gold, nickel-titanium and otheralloys thereof is easier to detect in such an image 4. Therefore, apossible momentary movement of the element 7 is also detectable and theirradiation equipment 2 may be adjusted to equalize such a momentarymovement.

The element 7 may also be of other biologically compatible materials,such as polymers and biological material being detectable in someimages.

The three-dimensional element 7 may have all kinds of shapes detectablein image 4 derived and produced by all kinds of medical imagingequipment, said shape resulting in a predefined geometrically structurein said image 4. In order to monitor a possible movement, the predefinedgeometrically structure is identified in the image 4 and the adjustingof the irradiation equipment 2 may either move the body or properlyadjust the position of other parameters of the irradiation equipment 2in response to this movement.

When using the aforementioned element 7 inserted in the urethra in thevicinity of the prostate the predefined geometrically structure may bethe diameter of the helically wound coil or the pitch distance betweenthe windings of the coil. This geometrically structure gives a number ofdetectable points and is automatically detectable in the image 4 byimage processing being implemented on a computer.

Another predefined geometrically structure of the element 7 may be theangle v between the straight part of the element 7 shown in FIG. 7 andthe conical part or the predefined geometrically structure may betransition point in which the straight part of the element 7 and theconically part of the coil intersect. This detection, like theaforementioned ways of detection, also provides a three-dimensionalpositioning of the element 7.

Elements 7 and other kinds of endoluminal prosthesis are oftenmanufactured in various lengths and the aforementioned predefinedgeometrically structure is independent of this variation in the lengthof stents and other endoluminal prosthesis.

The three-dimensional element 7 may, as mentioned above, possess allkinds of shapes giving a recognizable defined geometrically structure inthe aforementioned image 4. Examples of such other shapes are shown inFIG. 8-11. Instead of a helically wound kind of coil as shown in thesefigures the three-dimensional element 7 may be a tube having a solidwall and/or an expandable part or different kinds of locking mechanisms.The wall of the tubular element 7 can be made from wire being wound indifferent patterns, such as cross-patterns, knitting-patterns or thelike. The three-dimensional element 7 may, in another aspect of thepresent invention, be an implant or the reference may be such implant.

By the term mega-voltage equipment is meant all sorts of electronaccelerators operating over 150 kV, preferably above 1 MV, andpreferably below 50 MV. Such an electron accelerator may be theirradiation equipment 2 used for treating the patient by irradiating thetumor 6.

By medical imaging equipment is meant all kinds of equipment usable forproducing the image 4 of disordered tissue and the three-dimensionalelement 7. Such equipment may be Magnetic Resonance scan (MR-scan),Nuclear Magnetic Resonance scan (NMR-scan), Magnetic Resonance Imagescan (MRI-scan), Computerized Tomography scan (CT-scan), Cone BeamCT-scan, Positron Emission Tomography (PET), Single Positron EmissionComputed Tomography (SPECT), Single Positron Emission Tomography (SPET),Image-Guided-Radiation-Therapy (IGRT), Ultrasound-scan, or X-ray,high-energy photons equipment or high voltage equipment.

The term shape memory alloy is defined as a metal having transformationfrom martensite to austenite at a certain temperature range (AusteniteStart to Austenite Finish (AS to AF)). Within this temperature range (ASto AF) the expansion of the three-dimensional element 7 starts and theexpansion stops when all the martensite is transformed into austenite.The element 7 “remembers” at this temperature range (AS to AF) itsoriginal shape. At another temperature range (Martensite Start toMartensite Finish (MS to MF)) the alloy reverses to martensite. Belowthis other temperature (MF) the element 7 is easily deformable by handand the element 7 may therefore be easily deformable inside the bodycavity and retracted through the natural opening in which the element 7was inserted. Alternatively the element may be retracted through anothernatural opening than the one through which it was inserted. The shapememory alloy may also be called temperature-activated alloy.

The term shape memory alloy may also be a metal having super elasticproperties at a certain temperature, such as about 37° C., being thebody temperature, and a plasticity at a another temperature, such asbelow 0° C. By the wording super elastic properties is meant an alloywhich can be elastically deformed up to very high deformation ratescompared to other metals and which alloy does not necessarily have atemperature (AS) at which the material is capable of remembering anoriginal shape.

The shape memory alloy may be a nickel- titanium alloy, anickel-titanium-cobalt alloy, other transition and precious metal alloysor thermoplastic heat settable material exhibiting shape memorycharacteristics. Heating of the wire may be accomplished by inductionheating, immersion heating, application of RF energy, or by flushing thearea of the three-dimensional element 7 with a fluid at the specifiedtemperature.

1-47. (canceled)
 48. A method for identification of an element in two ormore images, the method comprising the steps of, identifying, in animage, a single integral three-dimensional element visible in the image,said single integral three-dimensional element being in position in ahuman body or an animal body in relation to a bodily matter of interestwithin the human body or the animal body, the method comprising thesteps of: identifying in a first image the single integralthree-dimensional element, visible in the first image, identifying in asecond image the same single integral three-dimensional element, visiblein the second image, collating the first image and the second imagebased on a determination of the position of the one and same singleintegral three-dimensional element in the first image and the positionof the one and same single integral three-dimensional element in thesecond image.
 49. A method according to claim 48, said method comprisingthe further step of, establishing a position and/or establishing anextension and/or establishing a shape of the at least one singleintegral three-dimensional element in reference to the bodily matter ofinterest within the human body or the animal body, the establishingbeing based on collating the first image and the second image.
 50. Amethod according to claim 48, where identifying the position of the atleast one single integral three-dimensional element is used also fordetermining at least one of the following physical characteristics inrelation to the at least one single integral three-dimensional element:A shape of the element and/or an extension of the element.
 51. A methodaccording to claim 48, wherein the two or more images, being derived bydifferent types of imaging equipments, are collated based ondetermination of at least one of the following characteristics of thesingle integral three-dimensional element, in each of the images: theposition or the extension or the shape of the element.
 52. A methodaccording to claim 48, wherein the two or more images, being derivedunder different set-up conditions when deriving the images, are collatedbased on determination of at least one of the following characteristicsof the single integral three-dimensional element, in each of the images:the position or the extension or the shape of the element.
 53. A methodaccording to claim 52, wherein the two or more images are derived with atime interval between the deriving of the images and are collated basedon determination of at least one of the following characteristics of thesingle integral three-dimensional element, in each of the images: theposition or the extension or the shape of the element.
 54. A methodaccording to claim 48, wherein the two or more images are being collatedautomatically, based on an automatic identification of the singleintegral three-dimensional element in the different images.
 55. A methodaccording to claim 53, wherein more images are derived with a timeinterval between the deriving of the images and are being collatedautomatically and continuously, based on an automatic identification ofat least one of the following characteristics of the single integralthree-dimensional element, in each of the images: the position or theextension or the shape of the element.
 56. A method according to claim48, said method comprising the further step of, setting up treatmentspecifications according to the information in the two or more collatedimages.
 57. A method according to claim 48, said method comprising thefurther step of, comparing at least one of the following characteristicsof the bodily matter of interest: the position or the extension or theshape of the matter, in reference to at least one of the followingcharacteristics of the single integral three-dimensional element, ineach image: the position or the extension or the shape of the element.58. A method according to claim 48, said method comprising the furtherstep of, using at least one of the following characteristics of thesingle integral three-dimensional element: the position or the extensionor the shape of the element, relative to a reference in the first imageas a reference-position, comparing at least one of the characteristicsof the single integral three-dimensional element: the position or theextension or the shape of the element, relative to the same reference inthe second image, with the reference-position in the first image
 59. Amethod according to claim 58, said method comprising the further stepof, guiding a treatment equipment according to the comparison of atleast one of the characteristics of the single integralthree-dimensional element relative to the reference in the second imagewith at least one of the characteristics of the single integralthree-dimensional element relative to the reference-position of the samereference in the first image.
 60. A method according to claim 59,wherein the treatment equipment to be guided is an external beam radiotherapy equipment.
 61. A method according to claim 57, wherein the samesingle integral three-dimensional element is used for setting Uptreatment specifications, based on collated pre-treatment images, andfor comparing at least one of the characteristics of the single integralthree-dimensional element, relative to a reference in one or morejust-before-treatment-images or in one or more during-treatment-images,with the reference-position in the pre-treatment images, and possiblythe step of guiding a treatment equipment, where the same singleintegral three-dimensional element possibly is used without re-insertionor re-positioning of the single integral three-dimensional element. 62.A method according to claim 48, wherein the imaging equipment is medicalimaging equipment such as Magnetic Resonance scan (MR-scan), NuclearMagnetic Resonance scan (NMR-scan), Magnetic Resonance Image scan(MRI-scan), Computerized Tomography scan (CT-scan), Cone Beam CT-scan,Positron Emission Tomography (PET), Single Positron Emission ComputedTomography (SPECT), Single Positron Emission Tomography (SPET),Image-Guided-Radiation-Therapy (IGRT), Ultrasound-scan, or X-ray,high-energy photons equipment or high/mega voltage equipment.
 63. Amethod according to claim 48, wherein the single integralthree-dimensional element (7) is intended for being placed and fixedinside a natural body cavity of the human body or the animal body.
 64. Amethod according to claim 63, wherein the at least one single integralthree-dimensional element is a tubular endoluminal prosthesis.
 65. Amethod according to claims 63, wherein the at least one single integralthree-dimensional element (7) is a helical coil of at least one wire.66. A method according to claim 48, wherein at least a part of the atleast one single integral three-dimensional element (7) has a shapeallowing passage of a liquid, gas or solid inside the cavity in whichthe element is in position.
 67. A method according to claim 66, whereinthe at least one single integral three-dimensional element is a tubularendoluminal prosthesis.
 68. A method according to claims 66, wherein theat least one single integral three-dimensional element (7) is a helicalcoil of at least one wire.
 69. A method according to claim 48, whereinsaid cavity has at least one surrounding wall, and wherein the at leastone single integral three-dimensional element (7) has a collapsibledesign enabling a collapsed design before the element (7) is positionedin the cavity, and enabling an expanded design when the element (7) isin position in the cavity.
 70. A method according to claim 48, whereinthe at least one single integral three-dimensional element (7) is inposition in the body preliminary to deriving the first image and thesecond image, said positioning of the element having been performedthrough a natural opening of the body (1) without substantiallypenetrating any tissue of the body (1).
 71. A system for carrying outthe method according to claim 48, comprising image deriving equipmentfor identifying a single integral three-dimensional element (7) in thefirst image and in the second image, image processing equipment foridentifying the position of the single integral three-dimensionalelement (7) in the first image and in the second image, image processingequipment for collating the first image and the second image, saidcollating being based on a determination of at least the position of theone and same single integral three-dimensional element in the firstimage and of at least the position of the one and same single integralthree-dimensional element in the second image.
 72. A system according toclaim 71, wherein the imaging equipment is medical imaging equipmentsuch as Magnetic Resonance scan (MR-scan), Nuclear Magnetic Resonancescan (NMR-scan), Magnetic Resonance Image scan (MRI-scan), ComputerizedTomography scan (CT-scan), Cone Beam CT-scan, Positron EmissionTomography (PET), Single Positron Emission Computed Tomography (SPECT),Single Positron Emission Tomography (SPET),Image-Guided-Radiation-Therapy (IGRT), Ultrasound-scan, or X-ray,high-energy photons equipment or high/mega voltage equipment.
 73. Asystem according to claim 71, wherein the at least one single integralthree-dimensional element (7) has a design enabling at least one of thefollowing operations: insertion and retraction of the element (7) withspecifically adapted endoscopic equipment.